A variety of data mining systems and methods are known for detecting associations among items stored or represented in a database. For example, in the context of an electronic catalog of items, data mining processes are frequently used to identify items that tend to be viewed, purchased, downloaded, or otherwise selected in combination by users. For instance, items may be identified as belonging to a frequent itemset if a relatively large number of users bought the items in combination during same transactions. Frequent itemsets are often utilized for recommending items to users who may share similar interests.